1. Field of the Invention
The present invention relates to a rotary valve apparatus used for the supply and discharge of a material to and from a high-pressure container in processing the material in the container.
2. Description of the Related Art
An example of the valve apparatus of this type is disclosed in U.S. Pat. No. 5,020,550. This conventional valve apparatus comprises a rotor housing, which has a rotor bore defined therein, an inlet connected to, e.g., the atmosphere, and an outlet connected to a high-pressure container. The inlet and the outlet are separated in the diametrical direction of the rotor bore. A rotor is contained for rotation in the rotor bore of the rotor housing. The rotor has a plurality of pockets on its outer peripheral surface.
Further, the rotor housing has pressurization-side communication ports arranged at intervals in a region extending from the inlet to the outlet, with respect to the rotating direction of the rotor, and depressurization-side communication ports arranged at intervals in a region extending from the outlet to the inlet. The corresponding communication ports on the pressurization and depressurization sides communicate with one another by means of equalizing pipes.
As the rotor rotates, each pocket of the rotor is connected to the inlet, pressurization-side communication ports, outlet, and depressurization-side communication ports, in succession.
Furthermore, the rotor housing is provided with pressure-regulating ports which are connected to each pocket immediately before the pocket reaches the inlet and outlet. The outlet- and inlet-side pressure-regulating ports are connected to the high-pressure container and the atmosphere side, respectively.
According to the valve apparatus described above, when a material is introduced through the inlet of the rotor housing, it is received from the inlet by one of the pockets. As the rotor rotates, thereafter, the material is carried toward the outlet of the rotor housing. The pocket, moving from the inlet toward the outlet as the rotor rotates, is connected successively to the pockets moving from the outlet toward the inlet by means of the communication ports and the equalizing pipes.
Every time each pocket moving from the inlet toward the outlet is connected to one of the pockets moving from the outlet toward the inlet, its internal pressure is increased by stages from the atmospheric pressure. When this pocket is connected to the outlet-side pressure-regulating port, its internal pressure becomes equal to the pressure in the high-pressure container. Every time each pocket moving from the outlet toward the inlet is connected to one of the pockets moving from the inlet toward the outlet, on the other hand, its internal pressure is reduced by stages from the level of the pressure in the high-pressure container. When this pocket is connected to the inlet-side pressure-regulating port, its internal pressure becomes equal to the pressure in the inlet, that is, atmospheric pressure.
Thus, when each pocket is connected to the inlet or the outlet, its internal pressure is on the same level as the inlet or outlet pressure. Accordingly, the material can be smoothly supplied from the inlet to the pockets and from the pockets to the outlet or the high-pressure container.
In consequence, according to the valve apparatus of this type, the loss of the pressure in the high-pressure container, that is, the rate of gas flow from the container through the apparatus, can be restrained as the material is continuously fed into the container.
If a gas in the high-pressure container is an inexpensive one, such as air or steam, the inlet-side pressure-regulating port may be simply opened to the atmosphere. If the handled gas is an expensive or special one, however, the gas released from the inlet-side pressure-regulating port should be collected in a recovery tank. In general, the gas recovered in the recovery tank is supplied to a booster, whereupon its pressure is increased to the level of the pressure in the high-pressure container. Thereafter, the gas is returned to the high-pressure container to be reused.
If the used gas is an expensive or special one, as described above, it should be circulated between the high-pressure container and recovery tank for the sake of economy. In order to reduce operating costs for this gas circulation, moreover, the capacity of the recovery tank and the capability of the booster should preferably be minimized.
The load on the equipment surrounding the recovery tank, booster, etc. can be lightened by only reducing the rate of gas circulation, that is, the rate of gas flow through the valve apparatus. To attain this, the pressure released through the inlet-side pressure-regulating port, that is, gas recovery pressure, must be lowered.
Every time one of the pressurization-side pockets, moving from the inlet toward the outlet, and one of the depressurization-side pockets, moving from the outlet toward the inlet, are connected to each other by means of the corresponding communication ports and equalizing pipe as the rotor rotates, their respective internal pressures are increased or reduced by stages, as mentioned before. Therefore, the gas recovery pressure, produced when each depressurization-side pocket is connected to the outlet-side pressure-regulating port, can be lowered by increasing the equalizing pipes and the communication ports in number.
If the numbers of the equalizing pipes and the communication ports are increased, however, the valve apparatus becomes more intricate in construction and bulkier, and the layout of the equalizing pipes is complicated.